In primates cortical area VI serves as virtually the sole channel through which visual information reaches the rest of the cerebral cortex and influences the conscious behavior of the animal. The substrates for sequential and parallel processing of visual information within VI have been shown by anatomical studies to be very specifically patterned. An understanding of these neural circuits is essential to the definition of how receptive field properties are generated. The intricate and stereotyped nature of these connectional patterns emphasizes the complexity of the controls, involving a series of molecular, cellular and functional interactions, that must come into play during development of the region. We will undertake anatomical studies, using Golgi impregnations, of he inhibitory circuitry within primary visual cerebral cortex of the monkey and in adjacent visual area V2; for comparison a similar study will also be made of the cat VI cortex to determine the generality of these patterns in mammalian visual cortex. The structural- functional relations of intrinsic network connections in monkey VI will be further examined using a combination of voltage sensitive dye mapping, to show patterns of functional activity, and anatomical tracing techniques designed to demonstrate the relation of connectional lattices to particular functional capacities. Physiological-anatomical correlations will be made of different types of thalamocortical projection neurons in the monkey lateral geniculate nucleus and of their terminal axons in the primary visual cortex using intracellular recordings and HRP injections via micropipette. Developmental studies, using neural transplantation techniques in rats and mice, will examine the events controlling laminar connectional patterns in the visual cortex; finally, the role of visual input in establishment of synapse populations in monkey visual cortex will be examined in tissue collected in previous project periods. The current interest in the functional logic of patterned cortical connections in visual cortex, in the formulation of computer models of mature and developing visual cortical function, and in the question of lineage versus environment as determinants of neuron structure and function, make an exciting framework for continued investigation of the region.